import type { MessageEventRouter } from "./MessageEventRouter.type";
import type { MessageEventMultiRouter } from "./MessageEventMultiRouter.type";

export function getRouterCallback<
  Router extends MessageEventRouter | MessageEventMultiRouter,
  Type extends keyof Router
>(router: Router, type: Type): Router[Type] {
  if ("function" !== typeof router[type]) {
    throw new Error(
      `MessageEvent type has no assigned callback: "${type}". Available keys are: "${Object.keys(router).join(
        '", "'
      )}".`
    );
  }

  return router[type];
}